Dragonfly Walk on the Thames Path - Part 2

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I was witness to a most amazing, real life, drama over the weekend. Continuing with my quest, on behalf of the British Dragonfly Society, to survey a square kilometre of the Thames from Swinford Lock, past the old canal and on up to the entrance to the River Evenlode, for the emergence of the rare Club-tail dragonfly. It is listed as ‘Near Threatened’ on the British Red List. Past experience over the last couple of weeks suggests that they like the cover of the wooded section of the path, and where the water current slows in the meanders.

The vegetation has really shot up after this week’s rain, and the better temperatures. So I concentrate my searches in this area, negotiating narrow gaps down to the river’s edge. Once in place I start looking for the larva. The hope is to find one that has not emerged yet but I am happy to find empty exuvia too as this suggests activity for the survey.

Saturday’s walk was successful in finding one such specimen, not emerged, so I hang around for a bit, before making the decision to move on up the path to search for more, but to return to catch the emergence. This was a mistake, and I totally misjudged the timeframe of this process. By the time I returned only 15 minutes later it was all over and the teneral dragonfly was perched proudly atop a reed sunning himself. I could have kicked myself.The experience taught me a value lesson in patience, furthermore hardened my resolve to get another walk in on Sunday.

Sunday arrived and by 11:30 I was on the path again, this time determined to see the whole emergence process. It didn’t take long before we spotted the first larva. It was not in the most convenient location, directly under the shadow of a large willow, leaving only 2 feet of soggy river bank for me to kneel precariously on. But I was determined this time to wait it out, however long it took! What I was about to see was totally amazing, and yes this time the camera, and iPhone were prepped and ready to capture the whole process.

So before I share this experience, there’s one technical bit you should know. Dragonflies are unlike other winged insects, in that they do not have a pupal stage like butterflies for instance. So, what this means is they emerge as adults directly from the larvae form. The larvae emerge from the water, and start to breathe air. The emergence is generally synchronised in early species (the Club-Tail emerges around the second and third week of May.)The Club Tail is quite rare too, found only in several rivers in southern England and Wales (Thames, Arun, Severn, Wye and Teifi) hence the importance of monitoring numbers as best as possible. It breeds in unpolluted water, where rivers have good meanders that deposit alluvium. To identify one of these medium sized dragonflies, there are several things to look for. Firstly the adult has a gap between the eyes, this is not the case with other species. Second, the tail has two yellow sections on the lower part at the end of its tail (sections 8 and 9). They are yellow and black when fully mature, these colours are muted when first emerged (these are called tenerals). It is unlikely to be confused with any other UK species.

Anyway, enough of the technical stuff, back to the really exciting bit. Having ensconced myself on the muddy bank of the Thames I set up the camera ready for filming, just in time to record the initial part of the moult. The thorax, head first followed by the legs and the wing cases. At this point it should be noted that the larva has already secured itself firmly to the reed, a really significant point as later in the process there appear to be times that a ‘hands free’ style of emergence is adopted.

Then there is a pause, for about 5 minutes, giving the legs time to harden ready for the next stage. Then without warning there’s a flurry of movement as the body starts to ‘wave’ back and forth, the legs in the air and the body arching backwards as the dragonfly pushes and expands its abdomen up and out of the larva skin. It finally positions it legs to give it a secure foot hold on the vegetation or simply to the attached exuvia.

Over the next five or so minutes I watch in awe as the tail flicks free, and the body still flat (as per the larva form) starts to swell into a recognisable shape of an adult dragonfly. The wings too, until now just pointed structures above the thorax, start to expand. They’re super compacted but as they expand show a pale translucent colour with dark veins. They expand faster than the body to a point where they are the same length. To put this into context, the larva is only 25mm or one inch long, and by the time the dragonfly is fully expanded it is 50mm, (2 inches) double the size! The whole process probably took 40-50 minutes from the start of the emergence to getting to its first perch in the sun.

It is then time to find a suitable perch, and rest in a sunny spot. This is generally on the top of the reed that the larva originally attached itself to, but not exclusively. The young teneral climbs the stem slowly to the top, where it comes to rest. It can be there for 12 hours or more while it conditions itself for flight. The wings at this stage have opened and flattened out to the horizontal position.

When it’s ready for flight, the reason for its favoured emergence site becomes evident. The tree cover provides perfect cover, and plenty of ‘safe’ perches. I say safe, there are a lot of things at this stage of their lives that can go wrong. Firstly they do not move much, so would be easy prey for a passing tern, or other predator. I also experienced a case later in the walk where a teneral had taken flight but been caught in a spiders web. As they are clearly not as strong at this point in their lives it was struggling to release itself from the clutches of the web. Rightly or wrongly, in the name of conservation, I helped the young adult to escape and it flew straight to the top of the nearest hawthorn tree ready to fight another day.

We found 3 emerged, emerging or tenerals on Sunday, adding to the total making 5 to date. A successful mornings work I think. I really feel like a proud parent!

I now have the best part of 250 images to sort through and select the lucky few to go to print ready for the Dragonfly Collection of Framed Photographs that will soon be available at Dragonfly Framing dragonflyframing.co.uk .

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